[11] Río Portugués has a length of nearly 30 kilometers (19 mi) and runs south from the Cordillera Central mountain range into the Caribbean Sea.

[17] The toponymy, or origin of the name, comes from one of its first settlers, Pedro Rodríguez de Guzman, known as el Portugués ("the Portuguese") because his ancestry was from Portugal.

[21] The river then runs in a southerly direction parallel to PR-10 for most of its trajectory, crossing barrios Guaraguao, San Patricio, and Tibes.

It brushes barrio Machuelo Arriba on its southwestern corner after it crosses PR-10 just west of the intersection of PR-10 and PR-504, immediately north of the Ponce city limits.

From there it enters barrio Machuelo Abajo and continues south crossing Avenida Betances/Avenida Tito Castro (PR-14), at a point about half a mile west of the intersection of routes PR-12 and PR-14.

It continues south crossing Calle Guadalupe, at which point it divides barrio Quinto to the west and Machuelo Abajo to the east.

Several hundred feet further downstream, at Miguel Pou Boulevard–PR-1 and Puente de los Leones–Tricentennial Park, the river divides barrios Tercero and San Antón.

After crossing Calle Comercio, Río Portugués divides barrios Cuarto and San Anton, and continues its southerly course towards Avenida Las Américas (PR-163).

Roads are listed as the river flows from its origin in Ponce's Barrio Guaraguao in the north to the Caribbean Sea in the south (N/A = Data not available): For flood control purposes, in the 1970s Río Portugués was diverted by the U.S.

It then continued south behind the Governmental Center/Puerto Rico Police Ponce Area headquarters, and followed a trajectory almost parallel to Avenida Hostos (PR-123, formerly PR-10).

Taking a sharp easterly turn, Río Portugués enters barrio San Antón, and crosses route PR-12/Avenida Malecon about one quarter of a mile north of PR-12's intersection with PR-2.

Another one mile (1.6 km) of southerly flow and the river empties as a single stream into the Caribbean Sea just east of La Guancha, safely avoiding most low-laying populated areas.

Today, 42 acres (170,000 m2) of Río Portugués scenic easement in Adjuntas's humid forest are a protected entity of the Conservation Trust of Puerto Rico.